In the past, the time required to accurately measure the resistance (R), inductance (L) or capacitance (C) parameter(s) of an electronic item (such as a semiconductor, resistor, inductor or capacitor, or a circuit combination thereof) has been undesirably long. Prior art resistance measurement methods intentionally have been made slow in order to avoid errors created by the parasitic capacitances present in any measurement apparatus. Contemporary prior art capacitance and inductance measurement methods have been slow due to their use of sinusodial excitation in combination with bridge-type resonance circuits, which must be balanced during the measurement sequence. As a result, high speed measurement rates, in the order of 1,000 measurements/second, have not been achievable.
Therefore, it is an object of this invention to provide a new and improved electronic measurement method and apparatus.
It is a further object of this invention to provide a new and improved method and apparatus for measuring the resistance, inductance and capacitance parameters of electronic items.
It is a still further object of this invention to provide a high speed method and apparatus for measuring the resistance, inductance and capacitance parameters of electronic items.
Another disadvantage of prior art R, L and C parameter measuring methods and apparatus is their inability to accurately measure the parameters of in-circuit components. The primary reason for this disadvantage is that R, L and C testing requires some form of external excitation. If the voltage level of this excitation signal is above the actuation voltage level of active devices connected in-circuit with the component to be tested, the active devices are made conductive. This creates an erroneous result due to the opening of circuit paths that draw current away from the component to be tested. More specifically, when the open circuit paths draw the external excitation current away from the component to be tested, they accordingly modify any measurements being made. Because the additional current draw is unknown, the resulting measurements cannot be modified in a compensating manner. One way of avoiding this problem is to maintain the voltage level of the excitation signal beneath the activation voltage level of the active device or devices connected in-circuit with the component whose parameters(s) is (are) being measured. In the past, this technique has had the disadvantage that measurement accuracy has dropped when this procedure has been followed.
Therefore, it is a still further object of this invention to provide a new and improved method and apparatus for measuring the resistance, inductance and capacitance parameters of electronic components mounted in-circuit.
It is still another object of this invention to provide a method and apparatus for rapidly and accurately measuring the resistance, inductance and capacitance parameters of electronic components while said components are mounted in-circuit.